The present invention relates to a rotary valve to distribute fluid in various directions and collect fluid from various directions. More specifically it relates to a rotary valve used in adsorptive separation equipment having a plurality of adsorbent chambers, the rotary valve distributing fluid to a certain number of adsorbent chambers and at the same time collecting fluid from a certain number of adsorbent chambers.
The adsorptive separation technique currently available using a plurality of adsorbent chambers include those employing a simulated moving bed or pressure swing adsorption.
The adsorptive separation technique employing the simulated moving bed basically consists of a desorption zone, a purification zone and an adsorptive zone which are serially and circularly interconnected in that order. Each zone comprises one or, in most cases, plural chambers connected in series, each chamber being charged with adsorbent. The fluid to be treated flows through the adsorbent chamber in a single direction of from the desorption zone to the purification zone and then to the adsorption zone.
The respective zones for separating components of a fluid mixture function as follows.
Adsorption zone:
The fluid mixture is brought into contact with the adsorbent to selectively adsorb a strong adsorptive component of the fluid mixture, withdrawing a raffinate output stream containing week adsorptive component and desorbent material to be described later.
Purification zone:
The adsorbent that has adsorbed the strong adsorptive component in the adsorption zone is brought into contact with an extract stream taken out from the desorption zone and/or a highly concentrated strong adsorptive component to improve the purity of the strong adsorptive component on the adsorbent.
Desorption zone:
The desorbent material is brought into contact with the adsorbent to displace the purified strong adsorptive component and withdraw the extract output stream containing the strong adsorptive component and the desorbent material.
Now, the one of the plurality of adsorbent chambers located at the upstream end of the desorption zone, the purification zone and the adsorption zone may be periodically shifted so as to be located at the downstream end in the adsorption zone, the desorption zone and the purification zone respectively. Each time such shifting is made, it results in that the three zones undergo a countercurrent shifting relative to the fluid flow, whereby a component-separation of the fluid mixture can be carried out continuously.
In practice, the fluid inlet and outlet ports of each zone are concurrently shifted to the span of single adsorbent chamber in fluid flow direction to thereby obtain the same operation performance attained by the shifting of adsorbent chambers. That is to say, a simulated moving bed is thus obtained in which the adsorbent undergoes a countercurrent contact with the fluid flow to continuously separate the components of the fluid mixture.
In the above, supply and discharge of the fluid stream are operated with use of a rotary valve provided with a plurality of annular grooves or a plurality of switching valves.
In the case of simulated moving bed making use of a rotary valve, the operation is made with use of, for example, conduits or pipes operatively connecting together the rotary valve and adsorbent chambers, and the arrangement is, for example, such that the fluid stream is passed through annular grooves in the rotary valve into adsorbent chambers through the connecting pipes or conduits. By intermittently rotating the rotary valve at constant intervals of time, shifting is made of the position of the fluid inlet and outlet ports.
In general, the adsorptive separation technique using the simulated moving bed requires a large number of adsorbent chambers resulting in an increased pressure loss of fluid. Therefore, the pressure of the fluid flowing in the rotary valve becomes necessarily large. Further, as the number of annular grooves that constitute a part of the fluid passage through the rotary valve increases, the contact area between the rotor and the stator disk also increases so that a large force is required to keep the rotor and stator disks in close contact so as to provide a tight seal for the fluid flowing in the rotary valve. This in turn makes the design of the rotary valve complex and costly. In addition the possibility of fluid leakage still remains.